Final answer:
The valid subnet address is option a) 192.168.1.0
Step-by-step explanation:
The valid subnet address for an Ethernet port on a router that has been assigned the IP address of 192.168.1.0 would be option a) 192.168.1.0.
When setting up a subnet address, the subnet mask determines how the IP address is divided into network and host portions. The subnet mask 255.255.255.0 represents a Class C network, which is the appropriate class for an IP address starting with 192.168.1.